Question

Which is stronger acid Phenol or Cresol?

Answer 1

Phenol:

1. It is a white crystalline solid which is volatile with the molecular formula ${\mathrm{C}}_6{\mathrm{H}}_5\mathrm{OH}$.
2. This aromatic compound contains the Phenyl group (${\mathrm{C}}_6{\mathrm{H}}_5$) with the Hydroxy group ($\mathrm{OH}$).
3. It is a weak acid but it causes the chemical burn.

Cresol:

1. It is also known as Hydroxytoleune which contains a Methyl group with the Phenolic acid.
2. It is present either in solid or liquid because its melting point is closer to room temperature.

Strong acid:

1. Phenol is strong acid as compared to Cresol because of its high electron density.
2. Cresol has one electron-donating group and a methyl group, resulting in an increase in electron density in Cresol Oxygen because of hyperconjugation and the positive inductive effect. This makes proton loss less complicated as the $\mathrm{O}-\mathrm{H}$ bond becomes stronger due to the increase in electron density.
3. Due to the presence of the Methyl group and deprotonation reaction of Cresol, the conjugate base of Cresol becomes unstable.
4. Hydroxyl groups attached to phenol present a very strong resonating effect which increases the electron density of phenol as well as the acidity.
5. The reaction mechanism of Phenol and Cresol is shown below: